text: An early variation of this principle is called a balance siphon. This implementation has the two chambers arranged side by side on a balance-like device, with a counterweight attached to the heated chamber.  Once the vapor has forced the hot water out, the counterweight activates a spring-loaded snuffer which smothers the flame and allows the initial chamber to cool down thus lowering pressure (creating a vacuum) and causing the brewed coffee to seep in.